In the Compact Disc, referred to below simply as CD, used as a recording medium for contents data, such as musical numbers, the data obtained on 8-14 (eight-to-fourteen) modulation (EFM) are recorded by NRZI (non return to zero inverted) in which pulse polarities are inverted with [0] or [1]. Turning to the frame format for a CD, each frame is made up by 24-bit synchronization signals, followed by a 14-bit sub-code, followed in turn by recording data in which each symbol is made up by 14 bits. The sub-code is management data in which, prior to modulation, one symbol is formed by 8 bits, and which is stored in each frame. The respective bits of the sub-code are allocated to P to W, of which the sub-code P is used for example as a start flag for indicating the pause between musical numbers, the sub-code Q is used for recording e.g., the address information, and in which the remaining six sub-codes R to W are collected together and used e.g., for graphics.
Between the neighboring symbols, there are inserted three coupling bits. These coupling bits are used for evading violation of the EFM conversion rule when the symbols are connected together, and are selected so as to render the absolute value of the digital sum value (DSV) smaller.
In an optical disc, such as CD, there are occasions where discrimination data need to be post-recorded, after recording the recording data, such as contents data, in order to supervise the copyright of the recorded recording data. If this discrimination data is recorded as sub-code, one symbol in its entirety becomes a different one. For example, if the discrimination data is recorded in the sub-code Q, the sub-code P or the sub-codes R to W are changed, as a result of which the contents data, already recorded, become unreproducible.
The discrimination data, post-recorded on the optical disc, is recorded by fusing a light beam reflecting film by illuminating a light beam on the land on the substrate forming the optical disc, for not causing the reflection of the light beam, thereby forming a simulated pit.
Meanwhile, in the EFM, the minimum run length Tmin (minimum length between transitions) is set to 2, the maximum run length Tmax (maximum length between transitions) is set to 10 and coupling bits of [000], [100], [010] or [001] are inserted between symbols of 14-bit modulation patterns. If, in recording the discrimination data by changing the lands of the latter half of the modulation pattern into pits, [000] is selected as the succeeding coupling bits, it may be an occurrence that the maximum run length Tmax (maximum length between transitions) exceeds 11 after recording the discrimination data, thus violating the modulation rule.
In recording discrimination data, post-recorded on the optical disc, the recording position of the discrimination data is indefinite because the recording position may be a land or a pit depending on data ahead or in rear of the symbol in which to record the data. Since the pit is formed as a recess, it is low in reflectance, such that, if the reflective film is fused by illuminating a light beam in the pit area, the recording and/or reproducing apparatus is unable to detect the recorded data.
A DVD-ROM has been proposed as an optical disc currently used as a recording medium for contents data, such as music numbers. In the DVD-ROM, BCA (Burst Cutting Area) is defined to allow for recording, as additional information, the discrimination data for discriminating the main data, such as contents data.
The BCA is provided in an area of the disc different from the disc area where the main data, such as contents data, have been recorded. The optical disc, provided with the BCA, can be reproduced except by a dedicated recording and/or reproducing apparatus or a dedicated reproducing apparatus.
The discrimination data is recorded on the individual optical discs and, in order not to deteriorate the production efficiency, needs to be of a data volume such as allows for recording within a preset time interval, such as several seconds. On the other hand, if the recording speed in the recording apparatus is increased such that the data recording volume per unit time is increased, it becomes possible to increase the data volume of the discrimination data. Thus, in providing a new optical disc, the recording capacity of a recordable area for e.g., discrimination data is sometimes set so as to be larger than the data volume of the actually recorded data, in such case, it is necessary to record e.g., the data length of the discrimination data.